1. Field of the Invention
The present invention relates in general to the field of manipulating fluid flow and/or particle motivating force and is related to separation, concentration, transport, reaction and mixing apparatus, method and process. More particularly, the present invention relates to improved manipulation by bringing the present invention in contact with the solution. Moreover, the invention can be embedded into existing liquid-containing vessels such as well-plates and microarrays.
2. Description of the Related Art
(Note: This application references a number of different publications as indicated throughout the specification by one or more reference numbers within brackets, e.g., [x]. A list of these different publications ordered according to these reference numbers can be found below in the section entitled “References.” Each of these publications is incorporated by reference herein.)
Devices using electrokinetic properties (electrophoresis, dielectrophoresis, electroosmosis and electrothermal convection) have been used to manipulate fluids and particles.
Electrophoresis is a technique for manipulating components of a mixture of charged molecules (proteins, DNAs, or RNAs) in an electric field within a gel or other support. Under AC electric field, uncharged particles suspended in a dielectric media can be polarized and further manipulated. If the field is spatially inhomogeneous, it exerts a net force on the polarized particle known as dielectrophoretic (DEP) force [1]. This force depends upon the temporal frequency and spatial configuration of the field as well as on the dielectric properties of both the medium and the particles. Single frequency electric fields can be used to transport and separate particles.
Fluid motion can also be induced by applying an electric field onto a solution. The force driving the fluid thus originates in the bulk (buoyancy, electrothermal effect) or at the interface between the fluid and the device containing the fluid (electroosmosis).
The buoyancy generates a flow because of a density gradient. It can be produced by internal or external heating. An electric field is often used as internal energy source. Applied to a solution, part of the electric energy dissipates in the fluid by Joule effect and locally heats the fluid. Furthermore, local heating creates gradients of conductivity and permittivity. The fluid can then move under the influence of an electrothermal flow [2, 3, 4].
Under certain conditions (material properties, conductivity and permeability of the fluid and the device containing the fluid), ion layers develop at the fluid-surface interface due to chemical associations or dissociations and physical adsorption on or desorption from the solid surface. Ion layers can also be generated at the surface of electrodes where a potential is externally imposed. Applying an electric field with a tangential component to the layers moves the ions which carry the fluid along by viscous force. This process produces a bulk flow [2, 3, 4].
Coupled with an electrohydrodynamic flow, several electrode geometries have been designed as a tool to manipulate fluids and particles. Interdigitated castellated electrodes are, for instance, designed to trap and separate particles [5, 6]. Polynomial electrodes [7], planar electrodes [8, 9], quadripolar electrodes [27] or more complex geometries [10] have also been proposed.
Micro Technology Applied to Biological Problems
Massively parallel hybridization [11-13] improves the way many biological and medical analyses are performed both in research and clinical applications, but there is still a lack of an efficient multipurpose device. As sample volumes used in massive parallel systems become smaller and smaller (micro- to nanoliter or even smaller) it is more challenging to manipulate the fluids since the fluid viscosity dominates any convection. Multiple reports have shown that micromixing, transport or concentration improves hybridization reaction [14-16,17,18]. Micromixing can be achieved by ultrasonic agitation (the nucleation of bubbles creates small jets that enhance the mixing) [19] or by vortexing or agitating the solution and creating convection [20]. Micromixing can also be produced by surface wave generation [21] for instance.
What is needed then are improved methods, processes and general apparatus to efficiently and accurately mix, separate, concentrate, and transport small volume of fluids with or without particles (e.g., atoms, molecules, cells in biological and chemical assays) using combined fluid flow and/or electrokinetic methods. The present invention satisfies that need.